The invention relates to a device for influencing the inflow of gas into a gas bag of an airbag module.
Devices for influencing the flow direction of the gas emerging from a gas generator of an airbag module are known. It is thereby achieved that the gas bag is primarily inflated in a direction which is advantageous for protecting the vehicle occupant.
From U.S. Pat. No. 5,149,130 an airbag is known wherein thermal protection extends around the gas generator. This thermal protection has flaps, which, after detonation of the gas generator, open up and allow unrestricted flow of the gas into the airbag. The flaps are only connected to the thermal protection on one side.
Furthermore, from U.S. Pat. No. 4,178,017, guide plates are known which are mounted in front of the outlet openings of the gas generator. The guide plates are deformed by the gases emerging from the gas generator so that they release the outlet openings fully or in part.
A reproducible influence of the flow direction of the gases emerging from the gas generator is only possible with difficulty with these arrangements.
From U.S. Pat. No. 5,306,042 a device is known for controlling the unfolding of a passenger airbag. With this device a cover cap is provided over the folded gas bag and after detonation of the gas generator the cover is lifted away from the dashboard by the inflating gas bag and is swivelled about a predetermined angle. The cover cap is located between the gas bag and windscreen even after its lifting. This stops the gas bag from spreading out in the direction of the windscreen and the gas bag spreads out primarily in the direction of the vehicle occupant.
The drawback with this device is that the cover cap must have side guides in order to allow lifting and swivelling to the required extent. The cover cap is thereby significantly more complicated and expensive than conventional cover caps.
In order to influence the stream of gas emerging from the gas generator towards the gas bag, diffusers are also known. These are mounted between the gas generator and the gas bag. Thus from EP A 0 677 433 A1 a diffuser is known which has flow openings which are restricted by inclined guide plates. In this way the gas emerging upwards from the gas generator is deflected and first meets the side sections of the gas bag so that these are inflated first while the middle section inflation is delayed.
The drawback with such a diffuser is that the manufacturing costs are increased through the guide devices and that the structural height of the airbag module is increased through the protruding guide devices. This is however disadvantageous since, both in the steering wheel and in the remaining structural groups in which airbag modules are to be stored with the folded gas bag, there is little space available.
The object of the invention is to be able to influence the flow direction of the gas emerging from an inflation device and thus the inflow of the gas into the gas bag at lower expense and without the need for additional space in the area of the folded gas bag.
A device for influencing the flow of gas into a gas bag of an airbag module with an inflating device and a gas bag includes at least one component part between the inflating device and the gas bag. The component part is deformable under the pressure of the gas emerging from the inflating device and forms or releases at least one opening in the predetermined direction. The component part has a flap-like section which is defined at least in part by surrounding perforations in the component part, and between the flap-like section and the remainder of the component part there are overlapping slits between which at least one retaining tab is formed which connects the flap-like section to the remainder of the component part.
The retaining tab is provided opposite the hinge-like connection between the flap-like section and the remainder of the component part and is bent up under the action of the gas pressure. The swivel area of the flap-like section is defined by the retaining tab. The swivel area can be predetermined in size more particularly by the choice of length and shape of the retaining tab.
Diffusers can be used wherein during the manufacturing process no additional deformations are required for producing guide devices. The guide devices are first produced directly after activation of the inflation device by utilizing the pressure exerted by the gases. During manufacture of the diffusers, punched out areas are only to be provided to allow deformation of a corresponding component part.
An important advantage exists in that, owing to the production of the guide device only after activation of the inflation device, no additional stowage space is required for the airbag module.
The size and shape of the flap-like section is determined by the extension, shape and position of the perforations. It is expedient if the perforations are designed slit-like. The flap-like section can swivel on one or both sides in dependence on the desired flow direction of the gas.
An expedient embodiment of the present invention provides that the flap like section has on two opposite sides a continuous connection with the component part acting as a hinge and that at least one slit and retaining tab run in the flap like section parallel to these sides. With this embodiment the middle area of the flap like section is curved upwards under the influence of the pressurized gas. The retaining tab can preferably have an L, Z, U or T shape.
In order to influence the swivel area of the flap-like section in one embodiment, pressure compensating openings are provided in the flap-like section. Through the choice of size of these openings it is possible to influence the surface area load of the flap section through the pressurized gas and thus its swivel area.
In another embodiment, the component part with the flap section is preferably a constituent part of a gas collecting tube which encloses the inflation device. Compared to a conventional gas collecting tube it is only necessary to define the flap section through perforations or slit-like punched out areas in the gas collecting tube. Compared to a known gas collecting tube, no additional space is required.
In another embodiment, the component part with the flap section can however also be any other structural group between the inflation device and gas bag.
The flap-like section has a curved cross-sectional shape.
In another alternative embodiment, the component part has opposing side parts instead of a flap-like section, and at least one section can be moved away from another section under pressure of the gas.
In a further embodiment, at least one part of the deformable component part has a different stiffness from the other parts of the component part. If the two parts have the same stiffness the two parts are deformed and pressed away from each other more evenly. If however one part has a greater stiffness than the other part then one part is not or only significantly less deformed than the other part. This can be achieved for example by the provision of corrugations. The part with the greater stiffness which is not or little deformed serves as the guide device for the gas whilst the stiffness of the second part determines the size of the flow opening for the gas. The arrangement of at least one corrugation in at least one of the parts is also expedient because here a space is provided between the parts into which the gas can enter. The process of separating the parts and thus of releasing the flow opening is thereby assisted.
Different stiffness can also be achieved by choice of material and/or by different material thickness. The deformable component part preferably consists of metal. The component part can be deformed both plastically and elastically through the pressure of the gas flowing out of the inflation device.